On a standing pilot gas furnace the thermocouple must be replaced when?
its not positioned properly
The millivolt reading is 28 or above
the millivolt reading is 22 or below
the tip of the thermocouple is in the tip if the pilot flame is 3/8
natural gas pressure at the main line is recorded at 7" WC (water column), But at the gas manifold it reads 1.5 WC. What is most likely to be the cause of this?
A defective main line regulator
Too large of a gas valve
plugged burner orifices
A defective pressure regulator on the gas valve
A technician servicing a gas fired furnace notices that only four out of five ribbon burners are firing simultaneously . What could be the problem with the system?
Too much gas pressure
Too little gas pressure
Burners not aligned correctly
A defective gas valve
Technician A says if a combination gas valve needs to be replaced if there are 24 volts present to the gas valve and it will not open.
Technician B says that if a combination gas valve has a new thermocouple and the pilot will not stay lit the gas valve needs to be replaced.
Which technician is correct?
Both are right
Both are wrong
What should be the first step that a technician should take if the gas pressure at the manifold is too high?
adjust the pressure regulator clockwise
adjust the pressure regulator counter clockwise
replace the pressure regulator
replace the combination gas valve
If the glame is lifting off the burner port what should the technician do to correct this problem?
Adjust the primary air by closing the air shutter
adjust the primary air by opening the air shutter
replace the burner
decrease the min gas pressure.
a step down transformer is reading 0 ohms at its secondary winding. what is the possible cause of this problem?
An open primary winding
an open secondary winding
A shorted primary winding
A shorter secondary winding
when a fan centre relay needs to be tested for 124 volts, what two terminals are used when measuring for transformer output voltages?
Terminals "R" and "W"
Terminals "R" and "G"
Terminals "R" and "Y"
Terminals "R and "C'
On a call for heat what two terminals should be closed on the thermostat?
Terminals "R" and "C"
when a thermostat sub base fan selector switch is moved to the fan "ON" postition, what two terminals will close in the thermostat.
A new thermostat was recently replaced. The technician observes that the burner cycle is not long enough. the most likely cause would be?
A defective thermostat
Low gas pressure
the anticipator needs adjusting
A customer has replaced a mercury bulb thermostat but complains that the burners will not shut off and the house is getting too hot. The cause would be?
A defective limit control
The thermostat is not properly level
the anticipator is set too low
A bimetal fan control will not turn the indoor blower off. As a result cool air passes through the registers between furnace cycles. What is the possible cause of the problem.
The heating circuit is open on limit.
the fan control contacts are stuck open
the fan control contacts are stuck closed
there is a defective gas valve
residents are complaining of experiencing sumptoms of headaches, watery eyes and nausea.
Tech A says the heat exchanger is cracked
Tech B says the furnace may only need cleaning and the heat exchanger is possibly plugged.
Both are correct
Both are incorrect
A belt driver motor has recently been replaced but the furnace is shutting off on limit control. the most likely cause is that .
A. the motor is running in the wrong direction
the motor is defective
the motor is too large
the motor mount is not correct.
upon testing a motor winding for continuity the technician records 3 ohms. The winding resistance should be 8 Ohms. The technician concludes that:
The winding is open
The winding is shorted
the winding is grounded
the motor is within the satisfactory operating conditions
A run capacitor is tested with an analog meter. The needle moves towards zero then back to infinity. What is the condition of the capacitor?
The capacitor is open.
The capacitor is good
The capacitor should not be used
The capacitor needs to be of a higher mfd rating
The temperature rise of a particular furnace states that it should be between 35F and 65F. The furnace is operating at 20F temperature rise with the proper gas pressure at the manifold. What could be done to solve this problem.
Add more outside air to the basement
increase the indoor blower motor speed
Decrease the indoor motor blower speed
replace the air filter with a more efficient type.
A belt driven motor has been replaces, but quickly gets hot and stops just short of burning out. Which of the following could cause the problem:
A fan belt that is too tightly adjusted
A fan belt that has only 1" of slack between the pulleys
The pulley on the motor is too small
none of the above.
A combination fan/limit control has been replaced. The indoor blower motor runs too long and the residents complain of cooler airflow. The technician should:
Replace the control again
Adjust the limit setting
Lengthen the fan off setting.
Check the readjust the fan-off differential
A service call is made to a customer who complains that when his furnace ignites, the flame rolls out in front of the head exchanger.
Technician A says that it is due to poor draft possibly a blocked flue or heat exchanger
Technician B says that it has to do with the limit control or the fan switch control circuit.
Both Technician are correct
Both Technicians are incorrect
A customer complains of headaches, sleepiness and nausea.
Technician A finds a crack in the head exchanger and says that the furnace should be shut down.
Technician B says that the crack isnt too serious and the furnace can operate temporarily but it must be cleaned.
Tech A is correct
Tech B is correct
Both technicians are correct
Both technicans are incorrect
A technician is servicing a standing pilot gas-fired furnace. The complaint is that the burners are not lighting. where should the technician start trouble shooting the system?
At the transformer secondary and at the combination gas valve
At the transformer primary only.
At the primary limit control
at the fan limit controls.
On a spark ignition system, The spark for the ignition continues with no ignition of gas at the burners.
Technician A Concludes that the thermostat is defective.
Technician B Concludes that it is possibly the control module
Which is correct?
Both technicians are incorrect
Which of the following is the correct test for a faulty cable on a direct spark ignition system?
A voltage check
A continuity check
An amerpage check
none of the above
A customer complains that the burners light on her system, But then immediately shut down. The problem is most likely to be?
In the control module
in the control transformer
in the limit control
in the gas valve
Which of the following would not be a proper procedure to perform on a direct spark ignition system where the spark continues, the burners light and the flames are immediately extinguished?
Check that the sensor is positioned in the flame correctly
check for the proper flame rectification
check for a proper grounding terminal
check that there is proper gas flow to the pilot
A hot surface ignition system does not ignite the main burner. after measuring voltage to the igniter the technician should:
Perform a resistance test on the igniter
Replace the flame sensor
Replace the main gas valve
Replace the control module
The burners of a gas furnace that is equipped with a 115-Volt hot surface igniter lights for approximately 7's and then goes out. what is the problem that could cause this symptom.
A faulty igniter
A faulty transformer secondary winding
burner shutting off on high limit control
a faulty sensor
The burners on a furnace having a hot surface ignition system light up but quickly shut off.
Technician A states that after testing the gas valve he determined that it has shorter
Technician B Visually checked the flame sensor, cleaned it and performed a continuity test. he faults a dirty sensor.
Both Technicians are correct
The thermostat on a mid efficiency gas furnace with a hot surface ignition system is placed on a call for heat. The burners do not light, but the igniter does glow. Which of the following would be the next step to take when troubleshooting the system?
test the flame sensor
test the gas valve and the gas manifold pressure
test the primary limit control and the fan control
test the thermostat
The draft pressure switch on a mid effciency gas furnace with a hot surface ignition system is placed on a call for heat. the burners do not light, but the igniter does glow. Which of the following would be the next step to take when troubleshooting the system?
Test the flame sensor
test the gas valve and the gas manifold pressure.
a defective inducer draft motor
a defective flame roll out sensor
A high efficiency gas furnace will not stay in operation. The unit runs for approximately 5 min then shuts down by the main furnace controller with an open pressure switch flash code. which of the following is not a proper test to perform in this situation?
check the inducer draft motor
Check the furnace filter
Check for a restricted flue pipe
both a and c
A service call is made on a mid efficiency gas furnace. on a call for heat, the induced draft motor will not operate. what is the proper trouble shooting procedure that should be taken.
Check for control voltage at "G" and "C" terminals at the circuit board.
check for control voltage across terminals "W" and "C" at the circuit board.
check the control voltage at the induced draft relay
Both B and C
A high efficiency gas furnace that uses a controller will not energize the blower motor after a pre selected 45sec time on setting. Which of the following would be the most correct trouble shooting procedure?
measure the resistance across the furnace controller low speed terminal and common.
measure the resistance across the furnace controller high speed terminal and common
measure the voltage to the motor and test the run capacitor
measure the amperage on the blower motor and test the run capacitor.
when servicing a mid efficiency gas furnace the thermostat has been turned to the off position but the burners remain lit and the induced draft motor continues to operate. which of the following would be the most correct troubleshooting procedure?
determine if the thermostat is open and check voltage at the gas valve
check for voltage at the indoor blower motor.
replace the control module
check the ignition system
on a high efficiency gas furnace that uses a controller the indoor blower motor will not de energize after its pre selected off delay setting. which of the following is a logical repair for the system.
replace the run capacitor
replace the blower motor
change the speed setting on the control module
The burners on a gas furnace cycle for approximately 3 to 4 min. during a call for heat. the system does not provide adequate heat for the home.
Technician A has determind that a new thermostat has been installed and that the heat anticipator was incorectly adjusted
Technician B cleans the position of the flame sensor and claim that this was the fault
both are correct
both are incorrect
A gas furnace has recently been converted to LP gas. on a call for heat the furnace is not firing correctly and is starting to soot up. what would be the most likely cause for this problem?
Low LPG pressure
too long of a burner cycle
wrong orifice size installed
all of the above
when inspecting a gas furnace it is noticed that the burner flames are very small in height. what action should be taken by the technician?
replace the gas valve
replace the orifices
check the pressure and adjust the primary air shutters if needed
contact the utility company to replace the gas meter
a customer is experiencing a loud delayed ignition from his gas furnace.
Tech A says its possible that the gas valve is not opening or closing properly
Tech B claims that its possible that after the furnace had been cleaned the burner were not properly aligned.
A customer called in complaining that his indoor blower would not stop running. what is the most possible cause of this problem?
a defective blower motor run capacitor
contacts stuck open on the fan control
contacts stuck closed on the fan control
both A and C
after diagnosing a no heat call it has been determined that the induced draft motor is not operating.
Tech A says that it is the fault of an induced draft pressure switch
Tech B states that the indoor blower relay module is defective.
both are right
both are wrong
The burners on a gas fired furnace are continously lit and setting the thermostat to the off position doesnt not make any difference. What is a possible problem for this fault ?
a defective gas valve
a defective fan control
a limit control stuck in the closed position
a shorted secondary winding on the transformer
a customer complains that she has no head and that the furnace does nothing at all. she says that it is a mid efficiency gas furnace with an induced draft motor and a direct spark ignition system. which of the following would be likely place to start trouble shooting
check the fan door switch
check for a blown fuse
check for a defective furnace switch
on a hot surface ignition system the igniter does not glow. what would be the most likely cause of this fault.
a bad flame sensor
a bad gas valve
a bad closed pressure switch
a bad igniter
on a spark ignition system the spark is occurring but its pilot will not light. which one would you check?
terminals PV and MV/Pv for 24 volts
test for continuity of PV coil
test for the gas to the pilot line
the thermocouple on a furnace has just been replaced but the pilot light continues to go out. what test should a tech perform?
ensure that the pilot flame is engulfing the tip of the thermocouple 3/8"
test continuity of the main valve
test for voltage to the main gas valve
check for open limit control
an existing thermocouple has been tested with a millitvolt meter and has registered 13 millivolts. which of the following would be the correct action to take?
make sure that the thermostat is calling for heat
replace the thermocouple
replace the pilot gas valve
there is no problem with the thermocouple and it should be left alone.
what is an acceptable voltage for a thermocouple?
an indoor blower motor will run but it cycles on a internal overload protector using a digital meter.
Tech A states the meter read zero when placing it across the motors run capacitor.
Tech B states that the meter read OL when placing it across the run capacitor.
a furnace has been operating during the mild winters. during the cold days the 3 year old furnace doesnt provide continuous heat to satisfy the demand. the technician does a Btu input measurement by clocking the gas meter and finds the system within specifcations. the temperature rise is also within system limits which of the following would be the most correct diagnosis.
the furnace was undersized in heating capacity
the gas pressure needs to be increased
the duct work needs redesigning
during furnace operations the thermostat is quickly satisfied. the new furnace heats the entire house very quickly then shuts off on thermostat demand. which would be the most correct statement of this situation
the thermostat needs replacing
the blower speed should be increased
the furnace heating capacity is oversized
the duct system is too large
Two gas furnaces were installed. Both were 150 MBtu/H (150,000 Btu/H). Both furnaces may operate at the same. when one furnace is running all operations are satisfied. When both furnaces are operating at the same time the burner flames of both furnaces decrease in size. Which procedure is correct.
Replace the heating thermostat
Increase the gas pressure regulator of the first furnace
replace both gas valves
Determine if the gas piping layout is properly sized
On a natural gas to LPG furnace conversation
Tech A states only one burner orifice needs to be changing
Tech B states the orifices gas valve regulator spring and pilot orifice should be changed.
A draft test has been performed and it is indicated that there is an improper draft for the gas furnace that is being used. Whcih of the following would be the correct procedure to preform?
Increases the gas pressure
increase the inducer draft motor speed
check for chimney obstructions
replace the heat exchanger